Structural unit particularly for staircases



Jan. 21, 1969 J. s. w. BENNETT 3,422,924

STRUCTURAL UNIT PARTICULARLY FOR STAIRCASES Filed Nov. 8, 1966 Shet of 5IIWE T' R .4 nah/Ev:

Jan. 21, 1969 J. 5. w. BENNETT 3,422,924

STRUCTURAL UNIT PARTICULARLY FOR STAIRCASES Filed Nov. 8, 1966 I Sheet 2of :5V

5 3 4 5 g Q I 4/ M d 5 2 J 2 17 Q INUEHT R Jan. 21, 1969 5. w, NE3,422,924

STRUCTURAL UNIT PARTICULARLY FOR STAIRCASES Filed Nov. 8, 1966 Sheet ofs MM svwmy wM-Mw BENNE #TTOQMLE S United States Patent 36,692/66 US. Cl.182194 Claims Int. Cl. E04f 11/00; 1306c 7/00 ABSTRACT OF THE DISCLOSUREStructural units are provided which are particularly suitable forstaircases and other building structures involving a plurality of thestructural units, each of which is made up of a planar tread membersupporting frames on a portion of which the tread rests and wherein asupporting frame is secured at each end of the tread member. Eachsupporting frame has a pair of parallel spacedapart elongate arms one ofwhich is disposed at the front of the tread and the other of which isdisposed at the rear of the tread. The supporting frame is usually arigid rectangular closed frame, but may be of C-shape.

This invention relates to structural units more particularly forstaircases, and to staircases and other building structure assembledfrom such units.

The problems which are solved by units embodying the present inventionoccur particularly in the building and design of staircases, but theunits have useful application in structures other than staircases.

In the construction of most staircases nowadays, building regulationshave to be observed which regulate both the length of the staircase,projected onto the horizontal, and the angle at which the staircase runsto the horizontal. In these cases the most substantial variable is thetotal rise of the Whole stair i.e. the difference in level between theparts of the building being linked. Because of the regulation of all theother possible parameters it is not possible to mass-produce staircasesfor use in situations where the total rise will vary by more than a verysmall amount, because a fixed total length of mass-produced stringer torun between two floor levels would involve variation in angle, wheretotal rise are different, affecting the horizontality of the treads andthe relation between tread and riser, which are critical under theregulations. Alternatively, stringers of various lengths (which bydefinition could not be mass-produced) would involve complicateddispositions of the treads to ensure conformity with the regulations.

It is the object of the invention to provide structural units from whichthe staircase can be built up, which allows the assembly of thestaircase from them with adjustable rise between adjacent treads so asregularly to occupy the whole of the total rise of the staircase, thisbeing provided for in a manner which permits performance of the task bya relatively unskilled workman.

According to one aspect of the invention I provide a constructional unitparticularly for staircases consisting of a tread forming member securedat each of its ends to a base end portion of a support frame, thesupport frames each having a pair of parallel spaced-apart arms extend-"ice ing perpendicular to the general plane of the tread, one at thefront and one at the rear of the tread, and adapted when secured to anadjacent said unit to form a rigid structure. Preferably, the arms formthe opposite major sides of a rigid rectangular closed frame andpreferably the tread is supported within the frame to rest against theinner surface of one of the minor ends of the frame. Preferably theframe is formed from a single piece of metal bar, the free ends of thesingle piece being secured together at one corner of the frame. Theframe may, however, be open.

According to a second aspect of the invention I provide a structureassembled from units according to the first aspect, the support framesbeing fixed together by the upstanding arm at the rear of a tread of oneunit being fixedly secured to the upstanding arm at the front of a treadof a next unit so as to determine the rise (if any) between the treadswhen the structure is set up with the arms directed vertical. Preferablythe support frames are secured together at two spaced-apart positions,and it is preferred that the two spaced-apart positions shall be closelyadjacent to the position on each arm where the next adjacent frame partsfrom the arm of the frame to which it is secured. Provision may be madeat the upper end of the arms for securing a handrail to them.

Accodding to a third aspect of the invention I provide a staircasewherein vertical portions of separate structural units are securedtogether such as to stagger tread portions of these adjacent units apartby an amount representing the rise between the treads in the staircases.

Particular embodiments of the invention will now be described withreference to the accompanying drawings wherein:

FIGURE 1 is a perspective view of a staircase embodying the invention,

FIGURE 2 is a side view of the staircase of FIGURE 1,

FIGURE 3 is a perspective detail view,

FIGURE 4 shows the invention embodied as a bridge or gallery structure,and

FIGURE 5 shows a modified structural unit.

The staircase shown in FIGURE 1 is made up from a plurality of separatestructural units 1. In the present embodiment five such units are shownto form a short staircase, but it is to be understood that within thelimits of the strength of the material and the precise form of structureused, any number of these units may be secured together to form a selfsupporting staircase. The limits could be determined by any competentstructural engineer.

Each of the units consists of two rectangular support frames 2 formedfrom metal bar secured one each end of a tread forming member 3. Thetread forming member is suitably a plank of timber of a desiredthickness, of width front to back slightly greater than thecorresponding dimension of the frame so that a front portion 4 of thetread projects in front of the level frame to form a sill for the tread.In the present embodiment, the tread is secured above the bottom minoredge 5 of the frame to lie within the frame, resting on the innersurface of that base, and is secured thereby bolts passing throughregistering bores 6 in the tread and in the base 5. The tread and framemust be rigidly secured together so as to confer lateral rigidity of thestructure which is to be made up from the units. Subject to this thetread may be secured not within the frame but could be secured below itsbase either to abut or to be spaced from it.

A rectangular closed frame is formed by bending metal strip round a jigto make a rectangle with one angular corner, where the free ends 7, 8meet and are welded or otherwise firmly secured together, and threerounded corners. The radius of curvature at the round corners is small,for example half an inch. It is preferred to form the frame with theangular corner adapted to occupy the position shown in FIGURE 3, so thatwhen secured to an adjacent unit no crevice is left for collecting dirt.

The support frame could, however, be constructed in other ways (thoughtto be less economical) such as welding together four straight bars toform a rectangular closed frame, or bending a single bar into C-form tomake an open frame. But in each case, there must be provided a pair ofparallel upstanding arms perpendicular to the plane of the tread, one atthe rear of the tread and one at the front of the tread (in theembodiment shown these arms are the straight lengths 9 and 10, FIGURE 3)and means must be provided for maintaining these arms spaced rigidlyapart when formed into a composite structure. In the case, for example,of a C- shaped open frame (FIGURE a continuous major vertical arm 10' atone side of one unit has secured to it both of the shorter mutuallyinturned upper and lower vertical arms 9', 9" of the other side of anadjacent unit, to bridge the gap between their ends. In the present casethe arms are maintained spaced apart by the bottom minor edge 5 and thetop minor edge 11 of the closed rectangular frame.

The staircase structure is built up by placing units side by side with astagger between adjacent treads such that the requisite total rise isgiven. Then, while adjacent units are temporarily held together, boresare made through them at 12 and 13, FIGURE 3, and securing bolts passedthrough. Alternatively units may be welded or otherwise secured togetherat those positions (and also at additional points, if desired). Thepositions for securing together the adjacent units should be as farapart as possible along the abutting portions of adjacent supportframes. The dotted lines in FIGURE 2 through the points 12, 13respectively show how the effect of securing together the units is toset up a composite girder structure. The further apart these lines thestronger the girder for the means employed. It is preferred therefore toposition the points 12, 13 as closely as possible to where bottoms ortops of adjacent frames diverge from the abutting parts on therespectively adjacent units.

The frame is also bored at the top end portion, at 14, to receivesecuring bolts for securing a handrail 15. It is particularly suitableto use a handrail and clamping means which is disclosed and claimed inUK. specification No. 982,681.

It is not necessary that adjacent arms of adjacent units abut intimatelytogetherthey may be spaced apart by spacer collars such as 16, FIGURE 2,provided these are strong enough to satisfy the requirements ofrigidity.

The unit uppermost in the staircase is bolted securely to the upperlevel of the building, at 18, FIGURE 1, and the unit lowermost in thestaircase is supported against sliding movements along the ground, inthe present case by bolting to a wood block 17. A metal bracket may beused, alternatively, to secure the lowermost unit to the surface onwhich it stands.

To assemble the staircase from a set of such units, the total reiserequired is accurately measured and the number of units required so thatthe rise per tread is within a desired limit is calculated. The riserequired per tread is then accurately calculated and the units (or theirframes alone) laid on a floor with the frames horizontal, and securedtogether. The staircase is then placed in position and secured at footand head. The addition of a handrail confers extra rigidity. As can beseen from FIGURE 1, the frame part alone of a unit may be used 7 to forma handrail support conforming with the appearance of the rest of thestructure.

In FIGURE 4 there is shown a structure made up of units 1 in which thetreads 19 do not have forwardly or rearwardly projecting sill portions,and in which the units 1 are secured together at points 12 and 13 asbefore so that the treads 19 are co-planar. This way a galleryforming orbridging structure is achieved which may bridge a gap between spacedfloor portions 20. A handrail 15 may be fitted to the top of theguardrail formed by the frames 2 in the manner previously described.

Although treads of timber have been described, for use in certainapplications e.g. fire escapes, metal treads would be employed.

If particularly heavy loads are to be resisted, metal bracing membersmay be secured between the side of the support frames. One position forsuch braces is shown at 21 (dot dash lines, FIGURE 2). The braces areinclined to the edges of the frame and are welded or otherwise securedto the opposed uprights.

An important quality of a stair (or any structure) formed from theseunits is that once erected it can, if it were not welded or otherwisepermanently made up, be

(a) easily dismantled (b) compactly stored (c) reused (i) in a similarlocation (ii) in a new location having a different total rise butrequiring the same number of treads and risers as before.

(iii) in an extended form by the addition of extra units (iv) in areduced form by the subtraction of units (v) many times This is not tosay that the structure is in any way a temporary one. But it can be usedto fulfill a temporary function.

What I claim and desire to secure by Letters Patent is:

1. A structural unit having a generally planar tread, two open centeredsupport frames having a portion on which said tread rests, one securedat each end of the tread, each support frame having a pair of parallelspacedapart elongate arms, one said arm being at the front of the treadand one at the rear.

2. A structural unit according to claim 1 wherein the support frame is arigid rectangular closed frame of which the lowermost portionconstitutes the tread support.

3. A structural unit according to claim 2 wherein the tread is rigidlysecured within the frame to one side of the rectangle.

4. A structural unit according to claim 1 wherein the frame is formed ofa single piece of metal bar.

5. A rigid self-supporting structure comprising a plurality of unitseach constructed according to claim 1, a front said arm of one unitbeing secured to a rear said arm of an adjacent unit.

6. A rigid self-supporting structure comprising a plurality of separatestructural units secured together, each structural unit having afloor-member and two open centered support frames rising from the floormember in spaced relation thereto laterally spaced apart along the floorforming member, a rigid joint between the support frames and the floormember, each support frame having elements at the front of the floormember and at its back secured respectively to the said means at theback and front respectively of a corresponding support frame of anadjacent said unit.

7. A structure according to claim 6 wherein the said elements of thesupport frames are a first single arm at the front and a second singlearm parallel to the first at the back of the floor member, each singlearm being secured to an adjacent unit at least at two spaced-apartpositions.

8. A structure according to claim 6 wherein the said elements of thesupport frames are a single arm at one side and two shorter mutuallyinwardly directed arms both parallel to the single arm at the otherside, the two shorter arms being secured to the single arm of a saidsupport frame of an adjacent unit at, in total, at least twospaced-apart positions along that single arm.

9. A structure according to claim 7 wherein the support frames areclosed rectangular hollow frames.

10. A structure according to claim 8 wherein the support frames are eacha single piece of metal bar bent generally in the shape of a C.

References Cited UNITED STATES PATENTS Williams 1821 McClure 52-187Lyons 182-194 Nixon 1821 Hawkins 52182 Hager 52182 10 REINALDO P.MACHADO, Primary Examiner.

